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OT: Old Hi-Fi Schematics?

post #1 of 7
Thread Starter 
Hi All,

Anyone here have a source for old schematics?

My trusty old MCS (Yup, JC Pennys!) 3835 Integrated Amp lost the right channel and I want to fix her up.

I've tried Penny's and they sent me a card saying they don't have any repair info for a piece of equipment manufactured more than 20 years ago.

I had heard these were made by someone else for Penny's, anyone know for sure? If true I could try them for a schem.

TIA,
erix
post #2 of 7
It is sad but true that old service manuals are no longer available from the manufacture. Your only hope is to obtain service Data from http://www.samswebsite.com/photofact/pf_search.asp or similar aftermarket Document service. The JC Penny Audio Equipment was made by Pannasonic but thay will not be able to help you since thay also no longer offer parts and service data from 20 years ago 3 Years max for them. I had this problem with a Technics SU-V8 Intergrated amp i Bought in 1980 and i needed a part and pannasonic was unable to get one. so the Amp sit's in the Attic untill the Time I can find the part of a used unit to use for Parts. Those old Mass market Audio components are sure alot better than the Mass market stuff of Today By a long shot. I can understand why someone would like to keep them Running. So Good Luck. You can always service it without service data It just takes putting a light behind the PC board and note where the Foils go. Yes i have been Knowen to use this method to get a schematic of somthing i wanted fixed But it is Time consuming.
post #3 of 7
Thread Starter 
Thanx PPL,

No luck on Sams but I'll keep trying - worse comes to worse I'll hold it up to the light!

I think it's the Sanyo power amp chip, the STK0039.

Good to see you back!

ok,
erix
post #4 of 7
erix, I'd say It's either the power amp, capacitor, or something else low-level in the output stage. Try using a function generator and create some 10khz sines or something, and measure the output from the preamp circuitry, after the output (audio signal filtering caps) and at the input of the power amp. Pretty easy to trouble shoot and figure out whats going on. Use a scope to see if it's clean / functioning, and probe the output levels in amps/volts as well, to see if everything is normal. If it's the power amp thats done (looks in your case to be propritary) then it's all over.

Also, most of this can be eliminated by just listening in on the headphone jack, as this is usually just fed from the pre-amp stage and amplified with an op-amp or something simple like that. SOME amps use the power amps at a dropped level to drive phones, though, but that's very rare.
post #5 of 7
Thread Starter 
Xander,

Thanx for the debugging advice - I'll give it a whirl....

I am planning on replacing all the electros with Nichons and the films with WIMA's - maybe that'll do it.

This amp has no opamps, a handfull of MOSFETs (? they have 5 pins) a couple of 8 pin SIP something-or-others and the two Sanyo chips on a big heatsink.

The headphone jack is right next to where the speaker-out jacks connect ot the board and a couple of hefty resistors - yikes! Lo-Fi!

Plenty of room in the chassis to patch in a pre-amp fed opamp headphone amp. heh heh heh....

ok,
erix

P.S. Message to Jude and all: If this is in the wrong place let me know. If you know of a better forum to ask about it let me know as well!
post #6 of 7
erix, don't worry. It's the right place.

Those are indeed probably mosfets. The 8pin SIP packages are probably resistor arrays. From what you described with the output jacks and resistors, your headphone jack may be fed from the output stage of the power amp.
post #7 of 7
erix:The Sanyo data sheet for the stk-0039 is http://www.datadart.com/al/sanyo/Stk00.pdf
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